drivers/char/mem.c

   1 /*
   2  *  linux/drivers/char/mem.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  *  Added devfs support.
   7  *    Jan-11-1998, C. Scott Ananian <[email protected]>
   8  *  Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <[email protected]>
   9  */
  10
  11 #include <linux/mm.h>
  12 #include <linux/miscdevice.h>
  13 #include <linux/slab.h>
  14 #include <linux/vmalloc.h>
  15 #include <linux/mman.h>
  16 #include <linux/random.h>
  17 #include <linux/init.h>
  18 #include <linux/raw.h>
  19 #include <linux/tty.h>
  20 #include <linux/capability.h>
  21 #include <linux/ptrace.h>
  22 #include <linux/device.h>
  23 #include <linux/highmem.h>
  24 #include <linux/backing-dev.h>
  25 #include <linux/shmem_fs.h>
  26 #include <linux/splice.h>
  27 #include <linux/pfn.h>
  28 #include <linux/export.h>
  29 #include <linux/io.h>
  30 #include <linux/uio.h>
  31
  32 #include <linux/uaccess.h>
  33
  34 #ifdef CONFIG_IA64
  35 # include <linux/efi.h>
  36 #endif
  37
  38 #define DEVPORT_MINOR   4
  39
  40 static inline unsigned long size_inside_page(unsigned long start,
  41                                              unsigned long size)
  42 {
  43         unsigned long sz;
  44
  45         sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
  46
  47         return min(sz, size);
  48 }
  49
  50 #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
  51 static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
  52 {
  53         return addr + count <= __pa(high_memory);
  54 }
  55
  56 static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
  57 {
  58         return 1;
  59 }
  60 #endif
  61
  62 #ifdef CONFIG_STRICT_DEVMEM
  63 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  64 {
  65         u64 from = ((u64)pfn) << PAGE_SHIFT;
  66         u64 to = from + size;
  67         u64 cursor = from;
  68
  69         while (cursor < to) {
  70                 if (!devmem_is_allowed(pfn))
  71                         return 0;
  72                 cursor += PAGE_SIZE;
  73                 pfn++;
  74         }
  75         return 1;
  76 }
  77 #else
  78 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  79 {
  80         return 1;
  81 }
  82 #endif
  83
  84 #ifndef unxlate_dev_mem_ptr
  85 #define unxlate_dev_mem_ptr unxlate_dev_mem_ptr
  86 void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
  87 {
  88 }
  89 #endif
  90
  91 /*
  92  * This funcion reads the *physical* memory. The f_pos points directly to the
  93  * memory location.
  94  */
  95 static ssize_t read_mem(struct file *file, char __user *buf,
  96                         size_t count, loff_t *ppos)
  97 {
  98         phys_addr_t p = *ppos;
  99         ssize_t read, sz;
 100         void *ptr;
 101
 102         if (p != *ppos)
 103                 return 0;
 104
 105         if (!valid_phys_addr_range(p, count))
 106                 return -EFAULT;
 107         read = 0;
 108 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 109         /* we don't have page 0 mapped on sparc and m68k.. */
 110         if (p < PAGE_SIZE) {
 111                 sz = size_inside_page(p, count);
 112                 if (sz > 0) {
 113                         if (clear_user(buf, sz))
 114                                 return -EFAULT;
 115                         buf += sz;
 116                         p += sz;
 117                         count -= sz;
 118                         read += sz;
 119                 }
 120         }
 121 #endif
 122
 123         while (count > 0) {
 124                 unsigned long remaining;
 125
 126                 sz = size_inside_page(p, count);
 127
 128                 if (!range_is_allowed(p >> PAGE_SHIFT, count))
 129                         return -EPERM;
 130
 131                 /*
 132                  * On ia64 if a page has been mapped somewhere as uncached, then
 133                  * it must also be accessed uncached by the kernel or data
 134                  * corruption may occur.
 135                  */
 136                 ptr = xlate_dev_mem_ptr(p);
 137                 if (!ptr)
 138                         return -EFAULT;
 139
 140                 remaining = copy_to_user(buf, ptr, sz);
 141                 unxlate_dev_mem_ptr(p, ptr);
 142                 if (remaining)
 143                         return -EFAULT;
 144
 145                 buf += sz;
 146                 p += sz;
 147                 count -= sz;
 148                 read += sz;
 149         }
 150
 151         *ppos += read;
 152         return read;
 153 }
 154
 155 static ssize_t write_mem(struct file *file, const char __user *buf,
 156                          size_t count, loff_t *ppos)
 157 {
 158         phys_addr_t p = *ppos;
 159         ssize_t written, sz;
 160         unsigned long copied;
 161         void *ptr;
 162
 163         if (p != *ppos)
 164                 return -EFBIG;
 165
 166         if (!valid_phys_addr_range(p, count))
 167                 return -EFAULT;
 168
 169         written = 0;
 170
 171 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 172         /* we don't have page 0 mapped on sparc and m68k.. */
 173         if (p < PAGE_SIZE) {
 174                 sz = size_inside_page(p, count);
 175                 /* Hmm. Do something? */
 176                 buf += sz;
 177                 p += sz;
 178                 count -= sz;
 179                 written += sz;
 180         }
 181 #endif
 182
 183         while (count > 0) {
 184                 sz = size_inside_page(p, count);
 185
 186                 if (!range_is_allowed(p >> PAGE_SHIFT, sz))
 187                         return -EPERM;
 188
 189                 /*
 190                  * On ia64 if a page has been mapped somewhere as uncached, then
 191                  * it must also be accessed uncached by the kernel or data
 192                  * corruption may occur.
 193                  */
 194                 ptr = xlate_dev_mem_ptr(p);
 195                 if (!ptr) {
 196                         if (written)
 197                                 break;
 198                         return -EFAULT;
 199                 }
 200
 201                 copied = copy_from_user(ptr, buf, sz);
 202                 unxlate_dev_mem_ptr(p, ptr);
 203                 if (copied) {
 204                         written += sz - copied;
 205                         if (written)
 206                                 break;
 207                         return -EFAULT;
 208                 }
 209
 210                 buf += sz;
 211                 p += sz;
 212                 count -= sz;
 213                 written += sz;
 214         }
 215
 216         *ppos += written;
 217         return written;
 218 }
 219
 220 int __weak phys_mem_access_prot_allowed(struct file *file,
 221         unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
 222 {
 223         return 1;
 224 }
 225
 226 #ifndef __HAVE_PHYS_MEM_ACCESS_PROT
 227
 228 /*
 229  * Architectures vary in how they handle caching for addresses
 230  * outside of main memory.
 231  *
 232  */
 233 #ifdef pgprot_noncached
 234 static int uncached_access(struct file *file, phys_addr_t addr)
 235 {
 236 #if defined(CONFIG_IA64)
 237         /*
 238          * On ia64, we ignore O_DSYNC because we cannot tolerate memory
 239          * attribute aliases.
 240          */
 241         return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
 242 #elif defined(CONFIG_MIPS)
 243         {
 244                 extern int __uncached_access(struct file *file,
 245                                              unsigned long addr);
 246
 247                 return __uncached_access(file, addr);
 248         }
 249 #else
 250         /*
 251          * Accessing memory above the top the kernel knows about or through a
 252          * file pointer
 253          * that was marked O_DSYNC will be done non-cached.
 254          */
 255         if (file->f_flags & O_DSYNC)
 256                 return 1;
 257         return addr >= __pa(high_memory);
 258 #endif
 259 }
 260 #endif
 261
 262 static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 263                                      unsigned long size, pgprot_t vma_prot)
 264 {
 265 #ifdef pgprot_noncached
 266         phys_addr_t offset = pfn << PAGE_SHIFT;
 267
 268         if (uncached_access(file, offset))
 269                 return pgprot_noncached(vma_prot);
 270 #endif
 271         return vma_prot;
 272 }
 273 #endif
 274
 275 #ifndef CONFIG_MMU
 276 static unsigned long get_unmapped_area_mem(struct file *file,
 277                                            unsigned long addr,
 278                                            unsigned long len,
 279                                            unsigned long pgoff,
 280                                            unsigned long flags)
 281 {
 282         if (!valid_mmap_phys_addr_range(pgoff, len))
 283                 return (unsigned long) -EINVAL;
 284         return pgoff << PAGE_SHIFT;
 285 }
 286
 287 /* permit direct mmap, for read, write or exec */
 288 static unsigned memory_mmap_capabilities(struct file *file)
 289 {
 290         return NOMMU_MAP_DIRECT |
 291                 NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
 292 }
 293
 294 static unsigned zero_mmap_capabilities(struct file *file)
 295 {
 296         return NOMMU_MAP_COPY;
 297 }
 298
 299 /* can't do an in-place private mapping if there's no MMU */
 300 static inline int private_mapping_ok(struct vm_area_struct *vma)
 301 {
 302         return vma->vm_flags & VM_MAYSHARE;
 303 }
 304 #else
 305
 306 static inline int private_mapping_ok(struct vm_area_struct *vma)
 307 {
 308         return 1;
 309 }
 310 #endif
 311
 312 static const struct vm_operations_struct mmap_mem_ops = {
 313 #ifdef CONFIG_HAVE_IOREMAP_PROT
 314         .access = generic_access_phys
 315 #endif
 316 };
 317
 318 static int mmap_mem(struct file *file, struct vm_area_struct *vma)
 319 {
 320         size_t size = vma->vm_end - vma->vm_start;
 321
 322         if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
 323                 return -EINVAL;
 324
 325         if (!private_mapping_ok(vma))
 326                 return -ENOSYS;
 327
 328         if (!range_is_allowed(vma->vm_pgoff, size))
 329                 return -EPERM;
 330
 331         if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
 332                                                 &vma->vm_page_prot))
 333                 return -EINVAL;
 334
 335         vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
 336                                                  size,
 337                                                  vma->vm_page_prot);
 338
 339         vma->vm_ops = &mmap_mem_ops;
 340
 341         /* Remap-pfn-range will mark the range VM_IO */
 342         if (remap_pfn_range(vma,
 343                             vma->vm_start,
 344                             vma->vm_pgoff,
 345                             size,
 346                             vma->vm_page_prot)) {
 347                 return -EAGAIN;
 348         }
 349         return 0;
 350 }
 351
 352 static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
 353 {
 354         unsigned long pfn;
 355
 356         /* Turn a kernel-virtual address into a physical page frame */
 357         pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
 358
 359         /*
 360          * RED-PEN: on some architectures there is more mapped memory than
 361          * available in mem_map which pfn_valid checks for. Perhaps should add a
 362          * new macro here.
 363          *
 364          * RED-PEN: vmalloc is not supported right now.
 365          */
 366         if (!pfn_valid(pfn))
 367                 return -EIO;
 368
 369         vma->vm_pgoff = pfn;
 370         return mmap_mem(file, vma);
 371 }
 372
 373 /*
 374  * This function reads the *virtual* memory as seen by the kernel.
 375  */
 376 static ssize_t read_kmem(struct file *file, char __user *buf,
 377                          size_t count, loff_t *ppos)
 378 {
 379         unsigned long p = *ppos;
 380         ssize_t low_count, read, sz;
 381         char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 382         int err = 0;
 383
 384         read = 0;
 385         if (p < (unsigned long) high_memory) {
 386                 low_count = count;
 387                 if (count > (unsigned long)high_memory - p)
 388                         low_count = (unsigned long)high_memory - p;
 389
 390 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 391                 /* we don't have page 0 mapped on sparc and m68k.. */
 392                 if (p < PAGE_SIZE && low_count > 0) {
 393                         sz = size_inside_page(p, low_count);
 394                         if (clear_user(buf, sz))
 395                                 return -EFAULT;
 396                         buf += sz;
 397                         p += sz;
 398                         read += sz;
 399                         low_count -= sz;
 400                         count -= sz;
 401                 }
 402 #endif
 403                 while (low_count > 0) {
 404                         sz = size_inside_page(p, low_count);
 405
 406                         /*
 407                          * On ia64 if a page has been mapped somewhere as
 408                          * uncached, then it must also be accessed uncached
 409                          * by the kernel or data corruption may occur
 410                          */
 411                         kbuf = xlate_dev_kmem_ptr((void *)p);
 412                         if (!virt_addr_valid(kbuf))
 413                                 return -ENXIO;
 414
 415                         if (copy_to_user(buf, kbuf, sz))
 416                                 return -EFAULT;
 417                         buf += sz;
 418                         p += sz;
 419                         read += sz;
 420                         low_count -= sz;
 421                         count -= sz;
 422                 }
 423         }
 424
 425         if (count > 0) {
 426                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 427                 if (!kbuf)
 428                         return -ENOMEM;
 429                 while (count > 0) {
 430                         sz = size_inside_page(p, count);
 431                         if (!is_vmalloc_or_module_addr((void *)p)) {
 432                                 err = -ENXIO;
 433                                 break;
 434                         }
 435                         sz = vread(kbuf, (char *)p, sz);
 436                         if (!sz)
 437                                 break;
 438                         if (copy_to_user(buf, kbuf, sz)) {
 439                                 err = -EFAULT;
 440                                 break;
 441                         }
 442                         count -= sz;
 443                         buf += sz;
 444                         read += sz;
 445                         p += sz;
 446                 }
 447                 free_page((unsigned long)kbuf);
 448         }
 449         *ppos = p;
 450         return read ? read : err;
 451 }
 452
 453
 454 static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
 455                                 size_t count, loff_t *ppos)
 456 {
 457         ssize_t written, sz;
 458         unsigned long copied;
 459
 460         written = 0;
 461 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 462         /* we don't have page 0 mapped on sparc and m68k.. */
 463         if (p < PAGE_SIZE) {
 464                 sz = size_inside_page(p, count);
 465                 /* Hmm. Do something? */
 466                 buf += sz;
 467                 p += sz;
 468                 count -= sz;
 469                 written += sz;
 470         }
 471 #endif
 472
 473         while (count > 0) {
 474                 void *ptr;
 475
 476                 sz = size_inside_page(p, count);
 477
 478                 /*
 479                  * On ia64 if a page has been mapped somewhere as uncached, then
 480                  * it must also be accessed uncached by the kernel or data
 481                  * corruption may occur.
 482                  */
 483                 ptr = xlate_dev_kmem_ptr((void *)p);
 484                 if (!virt_addr_valid(ptr))
 485                         return -ENXIO;
 486
 487                 copied = copy_from_user(ptr, buf, sz);
 488                 if (copied) {
 489                         written += sz - copied;
 490                         if (written)
 491                                 break;
 492                         return -EFAULT;
 493                 }
 494                 buf += sz;
 495                 p += sz;
 496                 count -= sz;
 497                 written += sz;
 498         }
 499
 500         *ppos += written;
 501         return written;
 502 }
 503
 504 /*
 505  * This function writes to the *virtual* memory as seen by the kernel.
 506  */
 507 static ssize_t write_kmem(struct file *file, const char __user *buf,
 508                           size_t count, loff_t *ppos)
 509 {
 510         unsigned long p = *ppos;
 511         ssize_t wrote = 0;
 512         ssize_t virtr = 0;
 513         char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 514         int err = 0;
 515
 516         if (p < (unsigned long) high_memory) {
 517                 unsigned long to_write = min_t(unsigned long, count,
 518                                                (unsigned long)high_memory - p);
 519                 wrote = do_write_kmem(p, buf, to_write, ppos);
 520                 if (wrote != to_write)
 521                         return wrote;
 522                 p += wrote;
 523                 buf += wrote;
 524                 count -= wrote;
 525         }
 526
 527         if (count > 0) {
 528                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 529                 if (!kbuf)
 530                         return wrote ? wrote : -ENOMEM;
 531                 while (count > 0) {
 532                         unsigned long sz = size_inside_page(p, count);
 533                         unsigned long n;
 534
 535                         if (!is_vmalloc_or_module_addr((void *)p)) {
 536                                 err = -ENXIO;
 537                                 break;
 538                         }
 539                         n = copy_from_user(kbuf, buf, sz);
 540                         if (n) {
 541                                 err = -EFAULT;
 542                                 break;
 543                         }
 544                         vwrite(kbuf, (char *)p, sz);
 545                         count -= sz;
 546                         buf += sz;
 547                         virtr += sz;
 548                         p += sz;
 549                 }
 550                 free_page((unsigned long)kbuf);
 551         }
 552
 553         *ppos = p;
 554         return virtr + wrote ? : err;
 555 }
 556
 557 static ssize_t read_port(struct file *file, char __user *buf,
 558                          size_t count, loff_t *ppos)
 559 {
 560         unsigned long i = *ppos;
 561         char __user *tmp = buf;
 562
 563         if (!access_ok(VERIFY_WRITE, buf, count))
 564                 return -EFAULT;
 565         while (count-- > 0 && i < 65536) {
 566                 if (__put_user(inb(i), tmp) < 0)
 567                         return -EFAULT;
 568                 i++;
 569                 tmp++;
 570         }
 571         *ppos = i;
 572         return tmp-buf;
 573 }
 574
 575 static ssize_t write_port(struct file *file, const char __user *buf,
 576                           size_t count, loff_t *ppos)
 577 {
 578         unsigned long i = *ppos;
 579         const char __user *tmp = buf;
 580
 581         if (!access_ok(VERIFY_READ, buf, count))
 582                 return -EFAULT;
 583         while (count-- > 0 && i < 65536) {
 584                 char c;
 585
 586                 if (__get_user(c, tmp)) {
 587                         if (tmp > buf)
 588                                 break;
 589                         return -EFAULT;
 590                 }
 591                 outb(c, i);
 592                 i++;
 593                 tmp++;
 594         }
 595         *ppos = i;
 596         return tmp-buf;
 597 }
 598
 599 static ssize_t read_null(struct file *file, char __user *buf,
 600                          size_t count, loff_t *ppos)
 601 {
 602         return 0;
 603 }
 604
 605 static ssize_t write_null(struct file *file, const char __user *buf,
 606                           size_t count, loff_t *ppos)
 607 {
 608         return count;
 609 }
 610
 611 static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to)
 612 {
 613         return 0;
 614 }
 615
 616 static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)
 617 {
 618         size_t count = iov_iter_count(from);
 619         iov_iter_advance(from, count);
 620         return count;
 621 }
 622
 623 static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
 624                         struct splice_desc *sd)
 625 {
 626         return sd->len;
 627 }
 628
 629 static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
 630                                  loff_t *ppos, size_t len, unsigned int flags)
 631 {
 632         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 633 }
 634
 635 static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
 636 {
 637         size_t written = 0;
 638
 639         while (iov_iter_count(iter)) {
 640                 size_t chunk = iov_iter_count(iter), n;
 641
 642                 if (chunk > PAGE_SIZE)
 643                         chunk = PAGE_SIZE;      /* Just for latency reasons */
 644                 n = iov_iter_zero(chunk, iter);
 645                 if (!n && iov_iter_count(iter))
 646                         return written ? written : -EFAULT;
 647                 written += n;
 648                 if (signal_pending(current))
 649                         return written ? written : -ERESTARTSYS;
 650                 cond_resched();
 651         }
 652         return written;
 653 }
 654
 655 static int mmap_zero(struct file *file, struct vm_area_struct *vma)
 656 {
 657 #ifndef CONFIG_MMU
 658         return -ENOSYS;
 659 #endif
 660         if (vma->vm_flags & VM_SHARED)
 661                 return shmem_zero_setup(vma);
 662         return 0;
 663 }
 664
 665 static unsigned long get_unmapped_area_zero(struct file *file,
 666                                 unsigned long addr, unsigned long len,
 667                                 unsigned long pgoff, unsigned long flags)
 668 {
 669 #ifdef CONFIG_MMU
 670         if (flags & MAP_SHARED) {
 671                 /*
 672                  * mmap_zero() will call shmem_zero_setup() to create a file,
 673                  * so use shmem's get_unmapped_area in case it can be huge;
 674                  * and pass NULL for file as in mmap.c's get_unmapped_area(),
 675                  * so as not to confuse shmem with our handle on "/dev/zero".
 676                  */
 677                 return shmem_get_unmapped_area(NULL, addr, len, pgoff, flags);
 678         }
 679
 680         /* Otherwise flags & MAP_PRIVATE: with no shmem object beneath it */
 681         return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
 682 #else
 683         return -ENOSYS;
 684 #endif
 685 }
 686
 687 static ssize_t write_full(struct file *file, const char __user *buf,
 688                           size_t count, loff_t *ppos)
 689 {
 690         return -ENOSPC;
 691 }
 692
 693 /*
 694  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 695  * can fopen() both devices with "a" now.  This was previously impossible.
 696  * -- SRB.
 697  */
 698 static loff_t null_lseek(struct file *file, loff_t offset, int orig)
 699 {
 700         return file->f_pos = 0;
 701 }
 702
 703 /*
 704  * The memory devices use the full 32/64 bits of the offset, and so we cannot
 705  * check against negative addresses: they are ok. The return value is weird,
 706  * though, in that case (0).
 707  *
 708  * also note that seeking relative to the "end of file" isn't supported:
 709  * it has no meaning, so it returns -EINVAL.
 710  */
 711 static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
 712 {
 713         loff_t ret;
 714
 715         inode_lock(file_inode(file));
 716         switch (orig) {
 717         case SEEK_CUR:
 718                 offset += file->f_pos;
 719         case SEEK_SET:
 720                 /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
 721                 if ((unsigned long long)offset >= -MAX_ERRNO) {
 722                         ret = -EOVERFLOW;
 723                         break;
 724                 }
 725                 file->f_pos = offset;
 726                 ret = file->f_pos;
 727                 force_successful_syscall_return();
 728                 break;
 729         default:
 730                 ret = -EINVAL;
 731         }
 732         inode_unlock(file_inode(file));
 733         return ret;
 734 }
 735
 736 static int open_port(struct inode *inode, struct file *filp)
 737 {
 738         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 739 }
 740
 741 #define zero_lseek      null_lseek
 742 #define full_lseek      null_lseek
 743 #define write_zero      write_null
 744 #define write_iter_zero write_iter_null
 745 #define open_mem        open_port
 746 #define open_kmem       open_mem
 747
 748 static const struct file_operations __maybe_unused mem_fops = {
 749         .llseek         = memory_lseek,
 750         .read           = read_mem,
 751         .write          = write_mem,
 752         .mmap           = mmap_mem,
 753         .open           = open_mem,
 754 #ifndef CONFIG_MMU
 755         .get_unmapped_area = get_unmapped_area_mem,
 756         .mmap_capabilities = memory_mmap_capabilities,
 757 #endif
 758 };
 759
 760 static const struct file_operations __maybe_unused kmem_fops = {
 761         .llseek         = memory_lseek,
 762         .read           = read_kmem,
 763         .write          = write_kmem,
 764         .mmap           = mmap_kmem,
 765         .open           = open_kmem,
 766 #ifndef CONFIG_MMU
 767         .get_unmapped_area = get_unmapped_area_mem,
 768         .mmap_capabilities = memory_mmap_capabilities,
 769 #endif
 770 };
 771
 772 static const struct file_operations null_fops = {
 773         .llseek         = null_lseek,
 774         .read           = read_null,
 775         .write          = write_null,
 776         .read_iter      = read_iter_null,
 777         .write_iter     = write_iter_null,
 778         .splice_write   = splice_write_null,
 779 };
 780
 781 static const struct file_operations __maybe_unused port_fops = {
 782         .llseek         = memory_lseek,
 783         .read           = read_port,
 784         .write          = write_port,
 785         .open           = open_port,
 786 };
 787
 788 static const struct file_operations zero_fops = {
 789         .llseek         = zero_lseek,
 790         .write          = write_zero,
 791         .read_iter      = read_iter_zero,
 792         .write_iter     = write_iter_zero,
 793         .mmap           = mmap_zero,
 794         .get_unmapped_area = get_unmapped_area_zero,
 795 #ifndef CONFIG_MMU
 796         .mmap_capabilities = zero_mmap_capabilities,
 797 #endif
 798 };
 799
 800 static const struct file_operations full_fops = {
 801         .llseek         = full_lseek,
 802         .read_iter      = read_iter_zero,
 803         .write          = write_full,
 804 };
 805
 806 static const struct memdev {
 807         const char *name;
 808         umode_t mode;
 809         const struct file_operations *fops;
 810         fmode_t fmode;
 811 } devlist[] = {
 812 #ifdef CONFIG_DEVMEM
 813          [1] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET },
 814 #endif
 815 #ifdef CONFIG_DEVKMEM
 816          [2] = { "kmem", 0, &kmem_fops, FMODE_UNSIGNED_OFFSET },
 817 #endif
 818          [3] = { "null", 0666, &null_fops, 0 },
 819 #ifdef CONFIG_DEVPORT
 820          [4] = { "port", 0, &port_fops, 0 },
 821 #endif
 822          [5] = { "zero", 0666, &zero_fops, 0 },
 823          [7] = { "full", 0666, &full_fops, 0 },
 824          [8] = { "random", 0666, &random_fops, 0 },
 825          [9] = { "urandom", 0666, &urandom_fops, 0 },
 826 #ifdef CONFIG_PRINTK
 827         [11] = { "kmsg", 0644, &kmsg_fops, 0 },
 828 #endif
 829 };
 830
 831 static int memory_open(struct inode *inode, struct file *filp)
 832 {
 833         int minor;
 834         const struct memdev *dev;
 835
 836         minor = iminor(inode);
 837         if (minor >= ARRAY_SIZE(devlist))
 838                 return -ENXIO;
 839
 840         dev = &devlist[minor];
 841         if (!dev->fops)
 842                 return -ENXIO;
 843
 844         filp->f_op = dev->fops;
 845         filp->f_mode |= dev->fmode;
 846
 847         if (dev->fops->open)
 848                 return dev->fops->open(inode, filp);
 849
 850         return 0;
 851 }
 852
 853 static const struct file_operations memory_fops = {
 854         .open = memory_open,
 855         .llseek = noop_llseek,
 856 };
 857
 858 static char *mem_devnode(struct device *dev, umode_t *mode)
 859 {
 860         if (mode && devlist[MINOR(dev->devt)].mode)
 861                 *mode = devlist[MINOR(dev->devt)].mode;
 862         return NULL;
 863 }
 864
 865 static struct class *mem_class;
 866
 867 static int __init chr_dev_init(void)
 868 {
 869         int minor;
 870
 871         if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
 872                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 873
 874         mem_class = class_create(THIS_MODULE, "mem");
 875         if (IS_ERR(mem_class))
 876                 return PTR_ERR(mem_class);
 877
 878         mem_class->devnode = mem_devnode;
 879         for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
 880                 if (!devlist[minor].name)
 881                         continue;
 882
 883                 /*
 884                  * Create /dev/port?
 885                  */
 886                 if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
 887                         continue;
 888
 889                 device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
 890                               NULL, devlist[minor].name);
 891         }
 892
 893         return tty_init();
 894 }
 895
 896 fs_initcall(chr_dev_init);